1. Field of the Invention
This invention relates to a method for fabricating semiconductor devices, more particularly to a method for fabricating semiconductor devices with epitaxial structures.
2. Description of the Related Art
Currently, there are various semiconductor devices with epitaxial structures mainly manufactured through an epitaxial process. Taking an example of a vertical-conducting light-emitting diode (LED) shown in FIG. 1, the optoelectronic semiconductor device 1 comprises a conductive member 11, an epitaxial film layer 12 that is disposed on the conductive member 11 and that is to form an epitaxial structure 10 along with the conductive member 11, and an electrode 13 disposed on the epitaxial film layer 12 of the epitaxial structure 10. The epitaxial film layer 12 of the epitaxial structure 10 is formed through an epitaxial process. By virtue of electrical connection with the conductive member 11 and the electrode 13, electricity may be supplied to the epitaxial film layer 12 so that light may be emitted through an optoelectronic effect when the electricity is supplied to the epitaxial film layer 12.
When fabricating the optoelectronic semiconductor device 1 (i.e., the vertical-conducting LED), a sapphire (Al2O3) substrate, which has a better lattice match for an epitaxial film layer formed thereon and which is in the form of a wafer, and is selected to serve as a temporary substrate. Then, on the temporary substrate, the epitaxial film layer of gallium nitride (GaN) is epitaxially grown; a conductive layer serving as a permanent substrate is formed on the epitaxial film layer; and the temporary substrate is subsequently removed from the epitaxial film layer. Thereafter, a plurality of the electrodes are formed on a surface of the epitaxial film layer that is exposed after the temporary substrate is removed, followed by cutting into a plurality of the optoelectronic semiconductor devices 1.
In the above conventional process, the temporary substrate is removed from the epitaxial film layer using a laser lift-off process or a mechanical polishing process. However, the laser lift-off process involves relatively high fabrication costs. On the other hand, the mechanical polishing process is likely to induce residual stress that could damage the structure of the epitaxial film layer.